This is a phase II, single-center, double-blind trial that will randomize 138 prior CABG patients with an intermediate SVG lesion (30%-60% angiographic diameter stenosis) on clinically-indicated coronary angiography, and HDL-C<60 mg/dL to ER-niacin at a dose of 1500-2000 mg daily or matching placebo (containing 50 mg of niacin that can cause flushing but has no lipid lowering effect) for 12 months. All patients will receive a statin with goal LDL-C <70 mg/dL. Coronary angiography, intravascular ultrasonography (IVUS), and intravascular near-infrared intracoronary spectroscopy (NIRS), and optical coherence tomography (OCT) of the intermediate SVG lesion will be performed at enrollment and after 12 months in each patient, along with exercise stress testing at 1 month and 12 months, B-mode carotid ultrasound imaging at enrollment and after 6 and 12 months, reactive hyperemia peripheral arterial tonometry (RH-PAT) at enrollment and after 6 and 12 months, and with peripheral blood sampling performed at enrollment and at 1, 3, 6, 9 and 12 months, to determine whether compared to placebo, administration of ER-niacin will result in: